Plant images

Plant biology

Skeleton weed is an erect, branched perennial herb growing to a height of 90 cm. Aerial growth dies in autumn with new rosettes appearing in autumn and winter.

Stems

Stems of skeleton weed are dense with downward-pointing bristles at the base. They are otherwise hairless except for a few stout hairs. Stems are wiry, ribbed with manybranches exuding a thick, milky latex when broken.

Leaves

Leaves of skeleton weed are mostly hairless and often with purple pigmentation.

The rosette leaves grow to 20 cm long, are deeply lobed with the tips of the lobes always pointing to the base of the leaf.

Skeleton weed leaves are similar in appearance to a dandelion leaf but the tips of these lobes point towards the tip of the leaf.

Skeleton weed sometimes lacks stem leaves. If present, they are small, narrow, inconspicuous, widely spaced and without teeth or lobes.

Leaves are variable in width and three distinct forms are present in Victoria. Broad and intermediate leaf forms have displaced the narrow leaf form which is well controlled by a rust fungus.

Flowers

Skeleton weed flowers have yellow florets and usually 9-12 ray florets in each head.

Petals are strap-like, toothed at the top and white streaked beneath, with heads 1-2 cm diameter.

Flowers have short stalks or sessile (have no stalks) and form in small clusters along the stems.

Seeds

The seeds of skeleton weed are white to dark brown, 3-4 mm long, ribbed with scales and tooth-like projections at the pappus end.

The pappus consists of toothed, white bristles 5-8 mm long on a stem or beak about the same length.

The white and yellow seeds of skeleton weed are usually sterile while olive-green to brown seeds are usually viable.

Growth and lifecycle

Method of reproduction and disperal

Skeleton weed reproduces from a long tap-root and by seed.

Most seeds germinate when placed on the soil surface, with 90 per cent germinating when covered with 6-7 mm of soil.

It has parachute-like seeds which are easily spread by wind. With their scales and tooth-like projections, the seeds become attached to wool and almost any fabric or material. They can also become caught in the crevices of machinery, vehicles and equipment. Contaminated hay and chaff have also been major modes of dispersal for this weed.

Cultivation is a major cause of local spread. When small patches are cultivated, the top 8-10 cm of roots are cut and dragged to clean areas. If soil moisture is adequate, these pieces produce fibrous roots and new plants develop.

Seed harvesting ants are also known to remove skeleton weed seeds and contribute to some local spread.

Seedbank propagule persistence

A single skeleton weed plant can produce more than 27,000 seeds in one season. Seed viability can be about 80 per cent, however, seeds are relatively short lived in the field and do not survive more than six months.

Preferred habitat

Skeleton weed prefers temperate, subhumid and semi-arid open scrublands occurring in dry situations on well drained sandy to moderately textured soils. It does not readily establish on heavy textured soils. The plant is tolerant to drought, frost and water-logging.

The icons on the calendar below represent the times of year for flowering, seeding, germination, the dormancy period of Skeleton weed and also the optimum time for treatment.

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Flowering

Seeding

Germination

Dormancy

Treatment

Impact

Impact on ecosystems and waterways

Skeleton weed grows best in open plant communities with minimal shading and root competition.

It is a weed of cultivation and open waste areas with disturbed soils.

It is palatable and nutritious in the rosette stage and during flowering until the stems become woody.

Agricultural and economic impacts

Skeleton weed's competition for nitrogen and other nutrients has significant impacts on agricultural yield and harvest costs.

Difficulty in controlling the weed also affects the value of the land. Light infestations can cause wear and tear to harvest machinery as well as delays through breakdowns. Heavy infestations can prevent harvesting as the plant's stems may become entangled so that many moving parts of the machinery become jammed. The sticky sap accumulates in harvesting machinery and slows grain movement adding to harvesting costs.

Social value and health impacts

Dense growth of the skeleton weed may produce a moderate negative visual effect and may prove to be a nuisance to people on foot.

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